1. Field of the Invention
The present invention relates to a rocker device for a micromechanical Z sensor, and to a method for manufacturing a rocker device for a micromechanical Z sensor.
2. Description of the Related Art
Conventional sensors for measuring physical acceleration usually have a micromechanical structure made of silicon (sensor core) and an electronic evaluation system. Sensor cores that enable measurement of an acceleration in a direction orthogonal to a principal plane of the sensor core are referred to as “Z sensors.” Such sensors are used in the motor vehicle sector, for example in ESP systems, or in the mobile telephony sector.
The aforesaid sensor principle is described in further detail, for example, in chapter 6 of the dissertation “Surface micromechanical sensors as electrical test structures for characterizing their manufacturing processes” [Oberflächen-mikromechanik-Sensoren als elektrische Teststrukturen zur Charakterisierung ihrer Herstellungsprozesse], Maute, Matthias; Universität Tübingen, 2003.
Published European patent application document EP 0 244 581 A1 discloses a micromechanical sensor for the purpose of automatic triggering of occupant protection apparatuses.
Published European patent document EP 0 773 443 B1 discloses a micromechanical acceleration sensor.
In the context of so-called “FP functionalization,” which is disclosed, e.g., in Published German patent application documents DE 10 2007 060 878 A1 and DE 10 2009 000 167 A1, a rocker that is not patterned only from a single compact layer, but instead is patterned in two different silicon layers, is configured for the micromechanical acceleration sensor. Movable “trough-shaped” structures can thereby be formed.
In the context of the handling of the acceleration sensor, upon a sudden overload (for example if a control device having the acceleration sensor falls to the ground), the mass and thus the spring can be deflected in a vertical direction (i.e. out of plane). A mass of an FP function layer can thereby tear out an upper electrode, or the FP function layer itself can be destroyed.
Mechanical stops that are described, for example, in Published German patent application document DE 10 116 931 A1 are proposed in order to prevent this. The stops disclosed therein block the rocker only after approx. 7 μm to approx. 10 μm. But because, in the context of the aforesaid technology with FP functionalization, the rocker is located between the two electrodes and they are less than approx. 2 μm apart from one another, this conventional overload protection is no longer sufficient. Additional structures that are capable of stopping the rocker prior to contact have therefore been developed. Mechanical stops of this kind are disclosed in Published German patent application document DE 10 2009 029 095 A1 and U.S. Pat. No. 8,124,895 B2.